This invention relates to the field of repairing major cuts or wounds in vehicle tires, which require vulcanizing a sizable patch to the interior of the casing and a plug of vulcanizing compound such as cushion gum in a skived portion of the cut or wound of the casing. Prior art methods of making such tire repairs included placing a repair patch in the damaged area of the tire and then curing by means of two electrical heating pads. During the curing process, the tire must be properly supported and various methods for supporting the tire have been used. One method has been to position a rigid core inside the tire to support one of the heating pads against the inside of the tire and to place an inflatable bag against the outside of the tire and over the other heating pad to hold it in place on the outside of the tire casing. The inflatable bag in such prior art method is mounted in a large heavy cavity mold which extends around the tire casing about one-third of its circumference. The inflatable bag is supported on the side which is away from the tire so the bag can be pressurized to place the outside heating pad against the tire and in turn the tire against the core and the inner heating pad. While this method is satisfactory in many respects, the cavity mold is a very heavy item of equipment which may weigh as much as several tons and is correspondingly expensive.
As for the rigid core placed inside of the tire in accordance with this previously known method, it may be typically either of aluminum or wood which are relatively heavy materials. Consequently cores for larger size tires become so large and heavy that they are difficult to handle by the workman. The cores for very large tires such as for earth moving machines may be as much as four feet long and two and one-half feet in diameter. Another major disadvantage of such cores used in the prior art method is that each core is useable with only one size of tire. Therefore, a large number of cores are required for a repair shop to be in a position to repair tires of various sizes which becomes expensive and also requires considerable storage space to keep a number of different size cores on hand.
The method and apparatus for repairing tires in accordance with the present invention overcomes a number of the problems associated with the prior art method. The method and apparatus disclosed herein is relatively inexpensive and comparatively lightweight, utilizing flexible sheet inflatable means both inside and outside of the tire casing to support flexible heating pads against both the inside and outside of the tire casing in the area of the patch. Furthermore, the flexible sheet inflatable means are held in place against the tire by a flexible belt or a girdle surrounding the patch assembly. Since virtually the entire patching materials and apparatus for holding it in place during the curing process consists of flexible sheet material, the weight is substantially less than that of the heavy cavity molds and cores used in prior art methods. Furthermore, by utilizing apparatus which is made of flexible sheet material, it is possible and relatively easy to adapt the same items for use in repairing tires of different sizes.
Another disadvantage of the rigid cavity molds and cores or mandrels of prior art methods is that they do not flex and conform to the exact circular configuration of the tire casing during the curing process. Therefore in order to maintain close contact between the rigid elements of the repair apparatus, comprising the core or mandrel on the inside and cavity mold on the outside, with the respective inner and outer surfaces of the tire casing it is necessary to use extra pressure at times which deforms the tire casing, even if only slightly. Such extra pressure during the curing process, and such deformation of the tire casing even though relatively slight, is enough to make the tire casing slightly "out-of-round" after the repair. The present invention overcomes this problem also, since the flexible sheet elements utilized in the present method readily conform themselves to the arcuate surface of both the inside and outside of the tire casing to maintain close intimate contact therewith by both the inner and outer heating pads throughout the curing process.